Golf club heads come in many different forms and makes, such as wood-type or metal-type, iron-type (including wedge-type club heads), utility or specialty-type, and putter-type. Each of these types has a prescribed function and make-up. The invention will be discussed as relating to iron-type clubs, in particular, wedge-type club heads, but the inventive teachings disclosed herein may be applied to other types of clubs.
Iron-type golf club heads generally include a front or striking face, a back, a toe, a heel, a top line, a hosel, and a sole. The front face interfaces with and strikes the golf ball. A plurality of grooves, sometimes referred to as score lines, is provided on the face to assist in imparting backspin to the ball. The portion of the front face where impact with the golf ball is intended is referred to as the impact area. The back can also be described as the back of the striking face and may vary in design, depending whether the iron-type golf club head is a blade, muscle back or cavity back design. The hosel is generally configured to have a particular look to the golfer, to provide a lodging for the golf shaft, and to provide structural rigidity for the club head. The sole of the golf club is particularly important to the golf shot because it contacts and interacts with the playing surface during the swing. The toe is the region of the golf club head that is distal to the shaft, while the heel is the region of the golf club head that is proximal to the shaft. The top line is the uppermost region of the golf club head, extending between the toe and heel of the golf club head.
In conventional sets of iron-type golf clubs, each club includes a shaft with a club head attached to one end of the shaft, and a grip attached to the other end of the shaft. The angle between the striking face and a vertical plane is called the loft angle. Usually, the shaft is oriented vertically when the golfer holds the golf club in the proper address position.
The United States Golf Association (USGA) publishes and maintains the Rules of Golf, which govern golf in the United States. Appendix II to the USGA Rules provides limitations for golf clubs. Several of these rules are particularly relevant to the design of the grooves and the striking face. For example, the following USGA rules regulate the geometry of the grooves: grooves must be straight and parallel; grooves must have a plain symmetrical cross-section and sides which do not converge; the width, spacing and cross section of the grooves must be consistent throughout the impact area; the width of a groove cannot exceed 0.035 inch; the distance between edges of adjacent grooves cannot be less than three times the width of the grooves and not less than 0.075 inch; the depth of each groove cannot exceed 0.020 inch; the cross-sectional area of a groove divided by the groove pitch must not exceed 0.0030 in2/in; grooves must not have sharp edges or raised lips; and groove edges must be substantially in the form of a round having an effective radius which is not less than 0.010 inch and not greater than 0.20 inch. Further, the surface roughness of the impact area cannot exceed that of decorative sandblasting or fine milling. The Royal and Ancient Golf Club of St Andrews (R&A), which is the governing authority for the rules of golf outside the United States, provides similar limitations to golf club design.
In 2008, the USGA announced the abovementioned new restrictions on groove design. Previous to 2008, the groove design rules were more lenient, which generally resulted in golf clubs, particularly wedges, with greater ball back-spinning capability. Under the pre-2008 rules, manufacturers generally used the same U-shaped groove design, with maximum allowable width, depth, volume, and number of grooves. Further, manufacturers generally utilized sharp radii on the edge of the grooves. The similar groove designs across the manufacturers were a direct result of consumer demand—golf club designers found that the maximum-sized grooves produced the greatest ball backspin.
However, as a result of the changes to the groove design rules, manufacturers are asked to stop manufacturing golf clubs that do not comply with the new groove design rules starting in 2011, but can sell inventory of these pre-2008 rules golf clubs through 2011. For golf professionals, they are required to compete using golf clubs compliant with the new groove rules as of Jan. 1, 2010. For amateurs, generally they may continue to use their pre-2008 rules golf clubs through 2024, after which they will be required to use golf clubs that conform to the new groove design rules. However, amateurs may be impacted as early as 2011, due to the likely unavailability of pre-2008 rules golf clubs, since manufacturers will likely stop manufacturing golf clubs that have grooves according to the old groove design rules, and will likely only sell golf clubs having grooves conforming to the current groove design rules.